X-rays from supernovae remants 3C 400.2 (≡ G53.7-2.2) and MSH 15-56

Detection of two new soft X-ray sources and their identification with the supernova remnants (RNRs) 3C400.2 and MSH 15-56, is reported. From the observed X-ray flux in the 0.7–2.0 keV energy range, the X-ray luminosity of 3C400.2 is derived to be in the range of (2.7–5.3)×10³⁵ ergs s^?1 and that of MSH 15-56 in the range of (0.9–1.6)×10³⁵ ergs s^?1. If we use the standard adiabatic shockwave model for the SNR's, an age of ～(1.4–3.2)×10⁴ yr is derived for 3C400.2 whereas MSH 15-56 is found to be younger of an age of (5–10)×10³ yr.